How drug tests work

Ever taken a test that you have to pee for? Well, you’ve either had a pregnancy scare or been drug tested. While there are elaborate ways to fake a drug test (see Rue’s method from Euphoria), honestly it’s probably not worth it. The likelihood is you’ll get caught and face more serious charges. We’re here to talk you through doing a *legit* drug test and what it means.

A group of young people are sitting around a desk. They are discussing drug tests. There is two women and one man. This is a full-body image.

How do drug tests work? 

One if the most common drug tests is urine drug testing. Basically, your body attempts to break down anything you put inside it, from food to drugs. ‘Metabolites’ are formed as part of this process. Drug testing looks for specific types of metabolites that are only present if you’ve been stoned. Keep in mind, these metabolites can stay in the body for long periods of time. So, if you had a rager a couple of nights back, odds are you’ll still be positive if your boss decides to test you. 

What are the detection times for a drug test to be positive?

If a tester had to name the most detectable drug, it would probably be cannabis. The active ingredient in cannabis is called THC, and the metabolites from THC can take up to 45 days to clear the body (depending on your body size and drug habit). Unfortunately, you can’t flush THC from your system overnight because it’s a non-water-soluble substance. Instead, it tends to get caught up in the body and released at a much slower rate.

Here’s a rough guide to some other drug metabolites that outstay their welcome, which urine testing can detect:

Hair drug testing

Drug metabolites can be detected in blood, perspiration and other body residue. Even with all those options, hair is an increasingly popular testing ground. Why? Because metabolites can supposedly filter out with hair growth and resist pretty much everything from shampooing to perm jobs. Figuring out if there’s drugs in your hair involves lab tests. Scientists have to dissolve the hair sample in a series of solvents that extract the illicit drug metabolites. Although, it should be noted that many people think these tests could be unreliable.

Can you fake drug testing results?

Short of shaving your head, or having a supply of drug-free wee to hand, there’s no sure-fire method to mess with drug tests. Even though many products on the market claim to beat the test, mostly by adding masking substances to your urine sample, nothing is 100% reliable. The means of detection is becoming increasingly sophisticated, so what might work one day might be useless the next.

But I’m innocent! 

Drug testing is still at the beginning stages of research. It’s believed that more than 250 over-the-counter medicines, and some food ingredients, could cause a false positive result. So, you can expect many legal disputes as drug testing in the workplace (UK) becomes more common.

Drug testing on arrest 

If you’re arrested for a ‘trigger offence’, you may be tested to find out if you’ve taken any Class A drugs. Trigger offences include: theft, robbery, burglary, motor vehicle-theft, handling stolen goods, possession of an illegal drug and possession of an illegal drug with intent to supply.

They can’t force you to provide a sample for testing, but be prepared to have a good excuse. It’s an offence to refuse a drug-test without a legitimate cause.

If you test positive for Class A drugs, you’ll be required to attend a compulsory drug assessment by specialist drug workers. The assessment will determine the extent of your drug problem, help you into treatment, provide medical advice and other support, even if you’re not charged with an offence.

Refusing to do either the test or subsequent assessment will set you back £2,500 and/or up to three months in prison.

Next Steps

  • Release offers free and confidential advice on everything to do with drugs and drugs law. 0845 4500 215
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  • Need help but confused where to go locally? Download our StepFinder iPhone app to find local support services quickly.

By Nishika Melwani

Updated on 25-Aug-2021